Area Forecast Discussion
Issued by NWS State College, PA-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KCTP 210345
Area Forecast Discussion
National Weather Service State College PA
1145 PM EDT Mon Mar 20 2017
A weakening cold front will pass through the region overnight.
A stronger cold front will move through Tuesday night bringing
sharply colder air for mid week. Temperatures will moderate
toward the end of the week into the weekend.
.NEAR TERM /UNTIL 7 AM TUESDAY MORNING/...
Regional radar still shows the remnants of an MCS diving SE
through southern Ohio into WV and eastern KY. To the north
rain showers are becoming a little better organized over Ontario
and the lower Gr Lakes. The HRRR still brings a slug of rain
into the region mainly between about 11PM and 4AM, keeping the
areal coverage limited and the QPF on the low side. Showers will
tend to dissipate toward morning leaving little more than
spotty drizzle. Overall I knocked POPS down a bit to better
match latest timing.
Temps should be mild overnight, running in the 30s. The coldest
air up north could lead to a rain/snow mix as the precipitation
tapers off late. Little or now accumulation is expected.
.SHORT TERM /7 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
High pressure will begin to build in for Tuesday. Clouds will
likely hang tough over the region for much if not all of the
day, but temperatures should be able to rebound a bit and
return to near or slightly above normal.
.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
Secondary/arctic front drops SSE across the region later Tuesday
night/Wednesday morning with much stronger cold advection in the
upper boundary layer (thanks to nearly orthogonal NW-NNW flow
of 25-35 kts to the isotherms in 925-850 mb layer).
The base of the subsidence inversion will be quite low (only
around 4 kft AGL) and the fetch over the upstream glakes will be
relatively short. So, the chance for significant LES will be
rather low. However, the shallow strato cu deck will reside
within the favorable DGZ thermal ribbon of -12 to -18C, so
light accums of snow (up to around an inch) should occur across
parts of the NW mtns and Laurel Highlands with just flurries
The coldest air we`ll likely see until sometime later next fall
will occur Wednesday into Thursday. Daytime highs and overnight
lows will be 12-15F below normal. Mins early Thursday will range
from near 10F along the PA/NY border, to the lower 20s in the
larger metro areas in the Lower Susq Valley as a nearly 1040 mb
sfc high drifts overhead. Some lows in the upper single digits
will be a good possibility in the perennial cold spots up north.
After a partly to mostly sunny and still rather cold day
Thursday (by late March standards), clouds will increase
Thursday night into Friday as a warm front drifts NE across the
commonwealth. Sfc temps, and temps aloft (850 mb) will be a few
to several deg C above freezing, so any light precip that occurs
with this front will be light.
The Warm front will likely lift into New York State and the warm
sector should expand NE cover the entire CWA Friday afternoon
through most of Saturday with temps surging well into the 40s to
around 50F Friday, then into the lower 50s (north) to lower 60s
(south) on Saturday.
Timing and location of the deep cold air and associated 1040+
sfc high over southeastern Canada will play a key role in the
storm track of a southern stream wave that will be sheared east
from the Mid Miss Valley late Saturday...through the Ohio River
Valley...Central Appalachians and Mid Atl Coast Sunday through
Pops for rain/showers will increase Saturday night through
Sunday night, but capped them off in the likely range at this
Shallow cold air could backdoor us from the NE later in the
weekend per the continued/consistent trend of the 12Z EC and
GEFS. This could lead to some precip type issues across
northern PA at a minimum.
.AVIATION /04Z TUESDAY THROUGH SATURDAY/...
-- Changed Discussion --Low pressure entering the Ohio Valley this evening will track
south of Pa late tonight, spreading rain showers and falling
CIGS across the region. Latest HRRR and SREF probability charts
suggest IFR conditions are possible between 10Z-14Z at JST/BFD,
MVFR conditions are likely at UNV/AOO and perhaps no sig
reductions at the lower elevations airfields of eastern Pa,
Any showers should push east of the region around 12Z, as the
low pressure system passes off the east coast. However,
residual low level moisture ascending the Allegheny Mountains
could create lingering MVFR stratocu at BFD/JST into early
afternoon. The arrival of high pressure and drier air should
result in widespread VFR conditions by late in the day, even
Wed-Thu...No sig wx expected.
Fri-Sat...Showers/reduced CIGS possible, mainly BFD.
-- End Changed Discussion --
NEAR TERM...La Corte